Gantry cranes are generally known for lifting and handling shipping containers and trailers. Such cranes are commonly equipped with wheels and rubber tires for manuvering on an asphalt surface of a shipyard, railyard or other intermodal facility. A mobile crane equipped with rubber tires is commonly referred to as an RTG (rubber tired gantry).
The Global Positioning System (GPS) is widely used for determining positions on the earth. As is known, the GPS includes a plurality of orbiting satellites that send encoded signals. By triangulating the signals of multiple satellites a GPS receiver can determine an XYZ position relative to the earth.
Conventional gantry cranes are manually driven by a human operator who occupies a cab of the crane. It has been desirable to provide a guidance system for a crane that enables the crane to automatically drive to a designated point, for example to the position of a container to be lifted. Although some crane guidance systems are known, including guidance systems that utilize GPS, an improved guidance system is needed to permit accurate automatic steering tracking as the crane travels along a curved path.